For several years now there has been a growing trend towards the integration of pollution-control means in the exhaust lines of motor vehicle engines.
Thus, for example, particulate filters or NOx traps are integrated in these lines in order to reduce the level of pollutant emissions in the environment.
The principle on which particulate filters work consists in trapping the particles emitted in the exhaust gases in order to retain them on the filter.
However, it is necessary to regenerate the filter periodically.
This regeneration is effected by the combustion of the trapped particles.
In order to achieve such combustion, it is necessary to combine a given number of conditions.
Thus, the temperature of the particles must be increased to a predetermined value known as the combustion-triggering value, this increase in temperature being brought about especially by an increase in the temperature of the exhaust gases on the output side of the engine.
However, the gases must also comprise a sufficient quantity of oxygen to ensure the smooth progress of this regeneration and optionally a given amount of unburned hydrocarbons, for example in a case where the particulate filter is catalysed or associated with a separate catalyst.
Specific systems for supplying fuel to engines have therefore been developed in the prior art.
These supply systems are in a form suitable for providing multiple fuel injections into the engine cylinders. These multiple injections comprise, for example, a pre-injection, a principal injection and a post-injection of fuel during the expansion phase of the corresponding cylinder.
The problem associated with using that type of system resides in the fact that the exhaust gases have a low oxygen content, which is unfavourable to the combustion of the particles, that is to say, to the triggering and propagation of this combustion.
The object of the invention is therefore to solve those problems